A flow regulator is a device which modulates the rate of flow of liquid or gas in a pipeline. The gas typically is natural gas. The flow regulator is installed to reduce relatively high pipeline pressure to a reduced level. One such flow regulator is disclosed in U.S. Pat. No. 2,917,269 of the present inventor. The flow regulator worked well in the industry. This apparatus is directed to an improved version of equipment for the flow regulator. The improvement is directed to the downstream diffuser.
When a flow regulator is installed in a pipeline, it creates a significant amount of turbulence due to boundry layer separation. The gas flow is diverted into an annular flow by the imposition of the flow regulator body in the pipeline. This forms an annular flume with a central dead space immediately downstream from the flow regulator. The central dead space, being on the downstream side, tends to draw a significant portion of the flowing gas back on itself after passing through the regulator to thereby initiate eddy currents immediately downstream of the regulator. When such downstream eddy flows are formed, they fill the dead space and even degrade the high velocity flume that surrounds the dead space in the annular flow path. Eddy flows at the vortex consume energy which is converted to heat.
Throughput capacity of a flow regulator is, in part, limited by the velocity of the gas flowing through the regulator. This can hardly be increased inasmuch as gas velocity is a function of several factors but is primarily limited at a maximum equal to sonic velocity. Flow capacity is often seriously limited by downstream turbulence. The turbulence which occurs is, in part, a result of the flowing gas redistributing across the width of the downstream pipe section. Such turbulence thereby compounds annular limitation on the total throughput permissible with the flow regulator. It has been observed that any increase in downstream turbulence thus reduces the total throughput of the valve. Downstream energy wastage cannot be overcome, as, for instance, by decreasing line pressure downstream of the flow regulator.
The flow regulator also creates noise. The noise level is raised as turbulence increases. The present invention has the virtue of reducing noise by reducing turbulence. This reduces the amount of horsepower required to keep the product flowing through the line.
In addition to reducing the noise level, a reduction in turbulence increases recovery or the total throughput of the valve. Turbulence reduces recovery becauses it takes energy to keep a vortex created by the turbulence in motion. The converting of velocity energy (kenetic energy) back into pressure (potential energy) increases recovery. This is accomplished by a feature of the invention whereby turbulence is reduced to the extent that recoveries in the range of 80%-90% are possible.
The features described above are obtained in the flow regulator of the disclosure by a construction utilizing a transverse plate adapted to be clamped between a pair of flanges. The plate suports an upstanding tubular sleeve on the exterior of a centralized plug. The centralized plug supports an expandable inner valve. An annular space adjacent to the inner valve is incorporated, the gas flowing through the annular space. The transverse plate is drilled with a number of openings. The several drilled openings are located at the termination of the annular space downstream from the inner valve, the transverse plate being drilled with two or more sets of passages. They all extend to the annular space whereby the stream of flowing gas is picked up and distributed on passing through the several passages. The several passages have inlets collectively receiving the flow. The several passages outlet through the downstream face of the transverse plate, and they are directed so that a portion of the gas flows to the center axis of the pipe while another portion is directed toward the periphery. Collectively, the several passages have a cross-sectional area which enables the annular flow of gas to expand after regulation as velocity drops, and the passages are direted so that a fairly uniform wave front across the cross-section of the pipe occurs immediately downstream. One feature of this apparatus is that the inlets for the several passages divide and distribute the gas through the valve in the desired manner.
Another important feature of the present invention is the distribution of flowing gas toward the center line of the pipe downstream to reduce unwanted eddy flow, and thereby modify turbulence and noise. Turbulence and noise are both reduced.
one of the advantages of the present invention is the ability of the apparatus to pick up an annular flow of gas and convert the annular flow of gas into a wave front downstream from the regulator which is fairly well distributed across the cross-sectional area of the downstream pipe to smooth the transition with a reduction in turbulence and noise. An important factor regarding the present invention is the ability of the apparatus to match the flow capacity of the flow regulator immediately adjacent to the expandable element which achieves modulated flow with the downstream handling capacity. In other words, the flow regulator passes the maximum capacity of gas for a given size or design through the flow regulator with no need to operate the flow regulator in a derated manner as a result of downstream turbulence and the like.
With the foregoing in mind, the apparatus of the present invention is summarized as a flow regulator having a resilient or expandable central plug or element. This comprises a valve element or expandable body. It is captured between end faces on a stem so that compression thereof will expand the body radially outwardly. Expansion restricts an annular passageway within a sleeve which fits around the body. The sleeve defines a lengthwise annular passage through the apparatus surrounding the regulator valve element. This passage terminates at a transverse plate. The transverse plate is drilled with several passages. The several openings are formed in groups of two or more, the first group comprising a set of drilled holes through the transverse plate which define a circle and which open at the outlet or back end to direct flowing gas in laminar fashion along the walls of the downstream pipe. The second set of openings extend through the plate and open towards the center line axis of the downstream pipe. The second set of openings direct regulated gas toward the center of the pipe. They modify the downstream flume and thereby reduce or eliminate eddy flows. Moreover, they form a more uniform wave front downstream of the equipment.